1. Field of the Invention
This invention relates to fragment warheads, in particular, selectable initiation-point warheads generating directed fragment patterns.
2. Description of Related Art
Non-nuclear warheads kill a target by fragment impact. Symmetrical warheads with single point initiation systems generate a fixed, isotropic fragment distribution. Since a target, particularly an airborne target, generally occupies only a small portion of the area of fragment distribution, such warheads are inefficient kill mechanisms.
Many efforts have been made to improve warhead kill efficiency by directing the fragment pattern on detonation. These efforts have included mechanical reorientation of the warhead just prior to detonation, the use of shaped explosives or fragment casings, and the use of complex detonation and fusing systems.
Examples of previous efforts are discussed in U.S. Pat. Nos. 3,447,463; 3,598,051; 3,703,865; 3,796,158; 3,820,462; 3,960,085; and 3,978,796.
One prior effort is represented by U.S. Pat. No. 3,853,059 to Moe, which teaches a double-end initiation system. In such a system, a cylindrical explosive includes a detonator at each axial end thereof. Selective initiation of one detonator generates an isotropic conical fragment pattern and initiation of both detonators simultaneously generates an isotropic annular disc fragment patterns.
Each effort at developing a warhead having directed or aimable fragments has had certain drawbacks. The most common detriment of these prior systems has been the necessarily large size and/or weight of the system. Increased size or weight of a warhead system decreases the usable fragment volume and the weight and volume of explosives. For example, many known methods require fuzing systems which identify azimuthal direction to the target. Such systems are complex, heavy and voluminous.
Additionally, due to detonator safety requirements, many known devices include elaborate multiple detonator arrays incorporating complex safe-arming mechanisms. Most detonators require a mechanical barrier to be interposed between the detonator and the explosive to be detonated (also called the "main charge") for safety reasons; the weight and volume of the mechanical barrier and the mechanism rendering the barrier selectively removable detract from the available explosive and fragment content of the weapon system. See, for example, Moe, U.S. Pat. No. 3,853,059.
Many known detonators involve use of mechanical safe-arm devices in conjunction with a hot bridge wire or an exploding bridge wire generating single-point initiation. Where multipoint initiation is required for fragment dispersion, multiple single-point initiation detonators were required. Each such detonator required a separate mechanical safe-arm device. This substantially increased the cost and weight of the warhead and reduced its reliability.
To overcome the drawbacks of multiple separate detonators, combined detonating fuzes (CDF) have been used. Such CDF systems incorporate a single initiator connected by CDF to multiple boosters. See Moe, U.S. Pat. No. 3,853,059. Simultaneous or sequential detonation requires careful design of CDF connections, since the length of the fuze determines time of booster detonation. Again, the cost and weight of such a system is great and its reliability is a problem.
One recent development, as described in Coltharp, U.S. Pat. No. 4,334,474, improves upon the CDF system by providing simultaneous multi-point initiation along a line or over surface. Instead of using connecting fuze material, the system in Coltharp uses a mesh of exploding bridge wires which simultaneously detonate a secondary explosive, namely PETN, along a line or surface. The system in Coltharp, therefore, provides for simultaneous multi-point initiation but does not permit sequential multi-point initiation absent the use of a plurality of mesh initiators.
A more significant disadvantage in the Coltharp device is its use of PETN as the booster for the detonator. Known detonators make use of primary or secondary explosives as boosters. The primary explosive is more volatile than the secondary explosive and requires significant safety protections to avoid inadvertent detonation. Even where certain secondary explosives are used as boosters in a detonator, the level of volatility of these explosives requires the use of mechanical barriers between the detonator and the main explosive charge as a safety precaution against accidental detonation. Pursuant to Mil-Std-1316, PETN, although a secondary explosive, requires a mechanical barrier between it and the main charge. Thus, the device in Coltharp has the additional disadvantage of requiring the mechanical safe-arm structure not necessary in the subject invention.
The present invention provides a warhead having precise initiation point detonation which is capable of directing the fragmentation pattern to maximize the number and energy of fragments impacting a target. The unique structure of the invention, however, minimizes the drawbacks of conventional systems. The elimination of mechanical safe-arm devices greatly simplifies the warhead and makes it cheaper and lighter. The warhead of the invention, therefore, results in a higher kill probability for an interceptor system having a given warhead weight.